To expand on Ólafur's response, even if you could, you would find that a very large number of questions and answers contain code. And of those that don't, they may still contain code blocks used for formatting.

By contrast, if you need coding help, such a filter might omit the result you need merely because someone describes the procedure in prose rather than in a code block.

You can use http://statoverflow.com/sandbox. Query for posts with <code> in the body of the question and at least one joined answer. Note that the site is using data that's couple months out of date now, though.